Ion exchange system



NOV. 7, 1967 J. Z|EVERS ET AL ION EXCHANGE SYSTEM 2 Sheets-Sheet 1 Filed Feb. #5, 1965 QQm QNN

INVENTORS 6709 M4 Ex/ey dame: KHZ/eyelid Chan/es c/ We w/zsy ATTORNEYS NOV. 7, 1967 J Z|EVERS ET AL 3,351,488

ION EXCHANGE SYSTEM Filed Feb. 8, 1965 2 Sheets-Sheet 2 I ALVENTORS 6705 14 @z/ey c/ames E" Z'e 'z/er's Char/es (1 4/02/0149 United States Patent M 3,351,488 ION EXCHANGE SYSTEM James F. Zievers, La Grange, Clay W. Riley, Palos Heights, and Charles J. Novotny, Cicero, 11]., assignors to Industrial Filter & Pump Mfg. Co., Cicero, 111., a

corporation of Illinois Filed Feb. 8, 1965, Ser. No. 431,131 8 Claims. (Cl. 127-9) The present invention relates generally to ion exchange systems which remove undesirable components from liquid solutions, and it relates more particularly to a new and improved method and apparatus of the mixed resin type and employing a novel method and means for regenerating the resins after they have become exhausted.

Although the method and apparatus of the present invention has many dilferent applications, it is described herein primarily as used for the demineralization of the sugar juices or sucrose solutions obtained in a sugar refining process where the end product is in the liquid state. The manner in which the present invention may be used to demineralize water is also described in detail hereinafter.

Among other things, the refinement of sugar requires the removal of what is known in the art as the ash components, and, accordingly, the demineralization step in the refining process is known as de-ashing. While the impurities which make up the ash components vary with the nature of the raw sugar product which, for example, may be sugar beets or sugar cane, as well as with the areas in which such products are grown, some of the more common ash components which must be removed from the raw sugar liquor are magnesium sulphate, calcium carbonate, calcium sulphate, magnesium carbonate, potassium sulphate, silica, and traces of iron. By way of example, Louisianas cane sugars contain approximately 3% ash components in the raw sugar solutions.

In the ion exchange system of the present invention, the raw sugar solution is passed through a mixed bed of anion and cation resins wherein the ash components are converted to hydrogen and hydroxide which in turn combine to form water. When the resins become exhausted, they must be regenerated. The cation resin is regenerated with an acid such as hydrochloric or sulphuric and the anion resin is regenerated with a base such as caustic or ammonia. The columns which contain the resins during the regeneration process must, therefore, be made of material that will withstand the corrosive properties of these regenerative materials, and this generally requires that the columns be made of carbon steel with vulcanized rubber linings and with stainless steel trim, or that the columns be made entirely of stainless steel. In either event, the cost of the columns and of the associated valves and piping is extremely expensive.

Therefore, a principal object of the present invention is to provide a new and improved method for regenerating the exhausted resins used in an ion exchange deminerv alization process.

Another object of the present invention is to provide a new and improved method and system for demineralizing liquids.

Still another object of the present invention is to provide a new and improved method and apparatus for demineralizing sugar and other sucrose solutions.

A further object of the present invention is to provide a new and improved method and apparatus for demineralizing water.

A still further object of the present invention is to provide a new and improved method and means for separating the anion resin from the cation resin.

A yet further object of the present invention is to provide a new and improved method and means for separat- 3,351,488 Fatented Nov. 7, 1967 ing two granular materials having different respective specific gravities.

Briefly, the above and further objects are realized in accordance with the present invention by providing a single resin separating and regenerating unit for a multiplicity of service columns which respectively contain a mixture of anion and cation resins. The resin separation unit employs the raw sugar or sucrose solution to quickly separate the resins which have been transferred to such unit from the service columns. The rapidity of the separation process enables a relatively fast regeneration cycle so that the resins from the individual service columns may be individually and selectively regenerated without shutting down the system. Moreover, only the sepa ration and regeneration unit must be insensitive to the regenerating materials thereby appreciably reducing the overall cost of the system.

In accordance with another feature of the present invention, means are provided whereby each of the service col-umns need be shut down for no more than a few minutes during which time the spent resin is removed and a previously regenerated resin mix is placed in the column. The column may then be returned to the system and is operated while the spent resin therefrom is being regenerated. Also, there is provided in accordance with still another feature of the present invention means for measuring the quantity of ash removed by any service column from the raw sugar or sucrose solution.

Further objects and advantages and a betterunderstanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a portion of a sugar refining system embodying the several features of the present invention; and

FIG. 2 is a valve sequence chart useful in understanding the operation of the embodiment of the invention shown in FIG. 1.

Referring now to FIG. 1, there is shown a plurality of generally cylindrical service columns or tanks 10, 11, and 12, which are identical in construction and each of which contains a substantially homogeneous mixture of anion and cation resins. The columns 10, 11 and 12 each have a frusto-conical bottom portion and their size varies with the particular installation. Connected to each of the columns are inlet lines 14, 15 and 16, respectively, through which the mother solution, which may be a sugar or sucrose solution is pumped through a plurality of valved conduits 17 and 17', 18 and 18, and 1 and 19' for feeding the mother liquor into the bottom portion of the mixed ion exchange resins. Only two inlets are shown for each column but it will be understood that additional inlets equally spaced about the periphery of the tanks are generally provided. Suitable distributors such as those disclosed in copending applications Ser. No. 402,020 filed Get. 6, 1964 entitled, Mixed Bed Ion Exchange System, and now abandoned and Ser. No. 396,840 filed Sept. 16, 1964 entitled, Apparatus and Method for regenerating Materials, assigned to the same assignee as the present invention, may be located in the lower portion of the columns 10, 11, and 12 for equalizing the distribution of the mother liquor to the mixed resin bed. A plurality of outlets designated 20 and 20', 21 and 21, and 22 and 22' connect to outlet troughs 24, 25, and 26 which may be suitably connected by means not shown to a common outlet.

While only three service columns 10, 11, and 12 are illustrated in the drawing, it will be understood that additional columns may be provided in a single system depending on the economics of the situation. Moreover, inasmuch as each of the columns 10, 11 and 12 are identical, and certain of the other equipment which is associated therewith is also identical, only those parts of the system which operate in conjunction with the column only are described in detail and the similar components which operate solely in conjunction with the columns 11 and 12 are identified with like reference numerals with the suffixes a and b appended thereto.

When the anion and cation resins in the column 10 have become exhausted and must, therefore, be regenerated, the inlet valves 17 and 17' and the outlet valves 20 and 20' are closed, and a drain valve connected in a large diameter drain line at the bottom of the column 10 is opened whereby the spent resins and the mother liquor contained in the column 10 fall under the force of gravity into a measuring tank 32 disposed immediately below the column 10. At this same time a valve 34 connected in a large diameter line between the column 10 and a column 36 located immediately above the column 10 is opened to permit a mixture of regenerated anion and cation resins from the column 36 to fall under the force of gravity into the column 10 to replace the spent resins being simultaneously dropped into the column 32. Also, a valve 37 connected in a vent line 39 from the measuring column 32 is opened to facilitate the transfer of the resins into the column 32 by exhausting air from the column 32. When the spent resins from the column 10 have thus passed through the valve 30 and the measuring column 32 is filled to any desired level, the valves 36 and 34 are closed. All or part of resins in the column 10 have now been replaced with the freshly regenerated resins, and the valves 17, 17' and 20, 20' are opened to return the column 10 to the system. This resin replacement operation can be accomplished in no more than a few minutes whereby the down time for the service column 10 is negligible. In order to regenerate the resins now contained in the measuring column 32. a valve 38, disposed in a line connected to the bottom of the measuring column 32, is opened and a valve 42 and a valve 40 are also opened to supply high pressure air to the top of the measuring column 32. In other respects the column 32 is sealed from the atmosphere whereby the resin mixture and the mother liquor are driven or blown through the valves 38 and 42 and through a conduit 43 into the bottom of a separating and regenerating column 46 making up a part of the regenerating unit. The particular air pressure used for this purpose varies with the application but a pressure of 15 p.s.i. is satisfactory for use in a sugar refining process. During this phase of the operation wherein the resin mixture is transferred from the measuring column 32, a valve 44 connecting to a sewer line is opened to vent air from the column 46. The mixture of anion and cation resins and the accompanying raw sugar or sucrose solution is thus blown under pressure from the measuring column 32 into the separating and regenerating column 46, and when this transfer has been completed the valves 38 and 42 are closed thereby isolating the tank 46 from the service part of the system.

In order to separate the anion and cation resins from one another in accordance with one aspect of the present invention, the specific gravity of the mother liquor in the column 46 is adjusted to a value intermediate the specific gravities of the cation and anion resins. The cation resin may be a monofunctional sulfanated copolymer of styrene and divinylbenzene. A suitable cation resin is sold by Rohm and Haas under the trade name Amberlite IR120. It has a specific gravity of about 1.3. The anion resin may be a styrene type anion exchanger produced from styrene and divinylbenzene containing quaternary ammonium groups. A suitable anion resin is sold by Rohm and Haas under the tradename Amberlite IRA- 4018. The specific gravity of such anion resin is generally about 1.1. The specific gravity of 60 degree Brix sugar liquor at the temperatures normally encountered, which is approximately 120 degrees F., is about 1.3. Accordingly, it is necessary to lower the specific gravity of the sugar liquor to about 1.2. To this end, a given quantity of either a sweetening or a dilution liquid, such as water, at an elevated temperature, of for example, degrees F., and which is compatible with the process, is injected into the column 46 through a valve 48. At this same time a valve 49 is opened to inject air into the column 46 through a distributor 47 at the bottom. The air loosens the resin mix and circulates the liquid to quickly mix the diluting liquid with the mother liquor. The anion resin, being of lower specific gravity than the diluted mother liquor, completely rises or floats to the top of the column 46 and the more dense cation resins sinks to the bottom. This separation takes place both quickly and completely even though the sizes of the individual resin particles may vary substantially from one another.

With the two resins thus separated in the column 46 with an intermediate layer of the liquid the cation resin is now transferred to a regenerating tank 54. To this end a pair of valves 50 and 51 connected to the bottom of the column 46 are opened and a valve 63 is opened to vent air from tank 54, and a valve 52 is also opened to connect the top of the column 46 to a source of high pressure air. The valve 52 and the valve 50 are left open only long enough for the cation resin and a portion of the intermediate liquid level to pass out of column 46. The conduit 43 is sufficiently short in length so that it is completely filled with liquid before the anion resin reaches the bottom of the column 46. When the conduit between the valves 50 and 51 is filled with the liquid, the valve 50 and 51 and 63, are closed and the valve 52 is thereafter also closed. The cation resin has thus been blown from the column 46 to a regenerating column 54 connected to the valve 51. Where this operation is performed manually, a window may be provided adjacent the valve 51 so that the operator may observe the material flowing to the valve 51 and close it when the cation resin has passed therethrough.

The anion and the cation resins contained in the respective columns 46 and 54 include a substantial amount of the diluted mother liquor which is of value and should be saved. Therefore, in order to save most of this liquid, a sweetening oif operation is initiated by opening the valve 48 to supply heated water to the column 46. Also, a valve 55 connecting to the distributor 47 is now opened to convey the diluted mother liquor from the tank 46 back into the system or to a suitable reservoir. In like manner, a valve 57 connected to an overhead inlet of the column 54 is opened to supply heated water to the column 54 and a valve 58 is opened to connect a distributor 59 at the bottom of the column 54 to a diluted mother liquor reservoir or back to the system.

When the concentration of sugar or other mother liquid in the solution being exhausted from the columns 46 and 54 through the valve 55 and valve 58 decreases to a value below a predetermined maximum concentration, the sweetening off process is terminated by closing the valves 48, 55, 57, and 58 and a backwash cycle is initiated by opening a valve 60 which supplies water to the column 46 through the distributor 47. At this same time the valve 44 is opened in order to supply the water flowing through the anion resin in the column 46 to the sewer or other depository. In like manner, a valve 62 is opened to supply water through the distributor 59 into the bottom of the column 54 and a valve 63 connected in a line to the top of the column 54 is opened to convey the water flowing through the cation resin in the column 54 to the sewer. The backwashing operation is continued until the water flowing through the valves 44 and 63 has become clear. At this time the backwash cycle is terminated by closing the valves 44, 63, 60, and 62 and the regenerating cycle for both the anion and cation resins is commenced.

In order to initiate the regeneration cycle wherein suitable regenerative solutions flow through the resin beds in the columns 46 and 54, several valves as described hereinafter are opened. The anion resin in the column 46 is regenerated by opening a pair of valves 65 and 66 which are respectively connected in lines supplying water and an alkali solution. The water and alkali solution are mixed at a point downstream of the valves 65 and 66 and supplied to the column 46 at a location near the top of the anion resin in the column 46. A valve 68 connected between the distributor 47 and the sewer is opened at this time for draining the alkali regenerant from the column 46 during the regeneration cycle.

The cation resin in the column 54 is regenerated by opening a valve 70 connected between a supply of a suitable acid regenerant and the top of the column 54 and a valve 72 connected between a source of water and a point downstream of the valve 70 whereby the water and the acid passing through the valves 72 and 70 is mixed prior to entering the top of the column 54. A valve 74 connected between the distributor 59 and the sewer is also opened at this time to drain the acid regenerant solution to the sewer. The regeneration cycle continues until the respective resins have been regenerated. In a successful embodiment of the present invention, this has been found to take about forty-five minutes.

Upon completion of the regeneration cycle, the valves 66 and 70 are closed and the resins are rinsed of regenerant solutions by the continued flow of water through the resins beds. This cycle of the operation may be referred to as a displacement rinse. At the end of such rinse, a fast rinse cycle is initiated by opening the valves 48 and 57 which supply heated water to the tops of the columns 46 and 54. This fast rinse continues until the resins are suitable cleaned and this may be satisfactorily accomplished in approximately forty-five minutes. When the resins in the columns 46 and 54 have been completely rinsed and therefore do not contain any of the acid or alkali regenerant materials, the valves 43, 57, 65, 68, 72, and 74 are closed.

The resins are now transferred from the regenerating columns 46 and 54 and mixed before returning them in a mixed condition to the column 36. At the completion of the rinsing cycle, the columns 46 and 54 are respectively filled with water and the respective anion and cation resins. The water and the anion resin are transferred from the column 46 by opening the valve 52 and the valves 76 and 77 whereby the high pressure air from the valve 52 enters the top of the column 46 and blows the water and the anion resin through the valves 76 and 77 through a cyclone type filter 79 and into a mixing column 80 disposed directly above the column '36. In like manner, a valve 82 connected between the source of high pressure air and the top of the column 54 is opened and valves 84 and 85 are opened whereby the high pressure air entering the top of the column 54 blows the water and cation resin through the valves 84 and 8-5 and through a cyclone type filter 86 into the mixing tank 80. A valve 87 connected between a distributor 88 in the bottom of the tank 39 and the sewer is opened to drain off the water in which the resins from the columns 46 and 54 was contained. When the resins from the columns 46 and 54 have thus been transferred to the column 80 and the water has been drained therefrom through the valve 87, the valves 52, 76, and 77 are closed. In order to facilitate the transfer of the resins to the mixing tank 80, a ballfloat valve 90 is connected in a vent line to the top of the column 86 thereby to exhaust air being replaced by the resins and liquid.

In order to dry the water by an evaporation process from the surface of the resins, the valves 82, 84, and 85 are left open so that air is blown through the mix resin bed now disposed in the column 80. Thereafter, the valves 82 and 85 are closed and a valve 94 connected between the top of the mixing column 80 and a source of the sugar or sucrose solution or whatever the mother liquid happens to be is then opened for a suificient time to fill the column 80 with the mother liquid and the resin. The valve 94 is then closed and a valve 92 is opened in order to pass high pressure air through the distributor 88 into the bottom of the tank 80. In passing through the mother liquid and the resins in the column the anion and cation resins are mixed into a generally homogeneous mass. The valve 92 is then closed and a drain valve 96 connected in a large diameter conduit between the bottom of the mixing tank 80 and the top of the column 36 is opened and a valve 97 connected between the tops of the columns 36 and 30 is opened in order to provide an air vent to facilitate the transfer of the mixed resin and the mother liquor from the mixing column 80 into the supply column 36.

FIG. 2 is a table showing the sequence of operation of the valves in order to effect the operation described hereinabove. The first column indicates in sequence the individual steps in the cycle; the second column indicates the approximate time required for each step in a typical sugar refining operation employing the present invention, the third column describes each step by name; in the remaining columns an X indicates that the particular valve identified thereabove is open.

It may be seen that the contacting services columns 10-12 are cut out of operation only for about three minutes during the entire regeneration cycle and in a typical sugar refining plant it has been found that the resin in the contacting columns must be changed no more than once during each six to eight hour period of service. The total regeneration time; i.e., the time from when the resin is transferred to the regeneration units from the measuring column 32 and is returned to the mixing column 80 is ordinarily less than two and one-half hours. Accordingly, in this typical operation, one regeneration unit comprising the columns 46 and 54 will handle three mixed bed contacting columns. Of course, if desired, larger separation and regeneration columns 46 and 54 can be provided so that the resins from two or more contacting columns can be regenerated at the same time. In this way, one separation and regenerating unit can accommodate a greater number of contacting columns.

The present invention has been described above particularly in connection with a system for demineralizing sugar or sucrose syrups but it will be readily apparent to those skilled in the art that the invention has many more applications. For example, if the contacting beds are used for the demineral-ization of water, the mother liquid would be water and would have to have its density increased in the separating column 46 in order to separate the anion and cation resins. Sodium chloride may be used for this purpose. Inasmuch as sodium chloride is often used in the regeneration and/ or rinsing of the resins, an additional operating step may not be required. The salt rinsing step is merely terminated part way through and used to advantage to separate the anion and cation resins. One or both of the thusly separated resins can be transferred to a separate tank or tanks and the sodium chloride rinse operation continued. An important feature of the present invention is, therefore, the use of the mother liquid itself in the resin separation step thereby increasing the speed of operation of the regeneration cycle while, at the same time, providing a rapid and complete resin separation.

While the present invention has been described in connection with particular embodiments thereof, it will be understood that those skilled in the art may make many changes and modifications without departing from the true spirit and scope of this invention. Therefore, it is intended by the appended claims to cover all such changes and modifications which fall within the true spirit and scope of this invention.

What is claimed is:

1. A demineralization system for use in a sugar refining process, comprising a plurality of service columns each containing a mixture of anion and cation resins,

means for passing a sucrose solution through the resins 7 in said columns to remove ash components from said solution,

a first resin regenerating column,

control means including valved conduits for selectively transferring said resin mixture and a quantity of said sucrose solution from said service columns to said regenerating column,

means for adding a liquid to said regenerating column to adjust the specific gravity of the sucrose solution to a value intermediate the specific gravities of said anion and cation resins whereby one of said resins floats in said solution While the other settles out,

a second regenerating column,

means for transferring the settled-out resin to said second regenerating column While leaving the other resin in said first regenerating column,

means for then sweetening off the sucrose solution from said resin,

means for then regenerating the resins in said regencrating columns, and

means for thereafter mixing said resins together and returning them to said service columns.

2. A demineralization system according to claim 1 further comprising a plurality of measuring columns respectively associated with each of said service columns into which said resin mixture is transferred prior to being transferred to said first regenerating column, and

a plurality of storage columns respectively associated With each of said service columns into which said resins are transferred after being regenerated and before being transferred to said service columns.

3. A demineralization system according to claim 1 wherein said first regenerating column has a resin capacity approximately equal to that of each of said service columns and no more than one 'pair of regenerating columns are provided for every nine service columns.

4. A demineralization system according to claim 1 further comprising means operative during the adding of said liquid to said regenerating column to adjust the specific gravity for injecting air into said regenerating column to loosen the resin mix and circulate the liquid being added.

5. A demineralization system comprising a service tank containing a mixture of anion and cation resins,

means for passing a liquid through said mixture to effect the removal of certain elements therefrom by ion exchange,

means for adjusting the specific gravity of said liquid to a value intermediate the respective specific gravities of said resins thereby to effect separation of said resins from one another,

means for holding the thus separated resins in independent containers so that they may each be regenerated separately.

6. A demineralization system according to claim 5 wherein said liquid is water and the specific gravity thereof is adjusted by adding sodium chloride thereto.

7. A demineralization system comprising a service tank containing a mixture of anion and cation resins,

means for supplying a liquid to said tank to effect separation of said resins, and

means for adjusting the specific gravity of said liquid to a value intermediate the respective specific gravities of said resins thereby to effect separation of said resins from one another.

8. A demineralization system according to claim 7 wherein said means for adjusting the specific gravity comprises means for introducing a liquid to said tank, and

means for simultaneously injecting air into said tank to loosen said mixture and circulate the liquid being introduced.

References Cited UNITED STATES PATENTS 2,692,244 10/1954 Kunin et a1 l2746 X 2,744,840 5/1956 Daniels et al. l2746 2,767,140 10/1956 Fitch 210--33 3,084,120 4/1963 Cecil et al. 210-33 3,130,151 4/1964 Levendusky 210-33 JOSEPH SCOVRONEK, Acting Primary Examiner.

MORRIS O. WOLK, Examiner.

E. G. WHITBY, Assistant Examiner. 

1. A DEMINERALIZATION SYSTEM FOR USE IN A SUGAR REFINING PROCESS, COMPRISING A PLURALITY OF SERVICE COLUMNS EACH CONTAINING A MIXTURE OF ANION AND CATION RESINS, MEANS FOR PASSING A SUCROSE SOLUTION THROUGH THE RESINS IN SAID COLUMNS TO REMOVE ASH COMPONENTS FROM SAID SOLUTION, A FIRST RESIN REGENERATING COLUMN, CONTROL MEANS INCLUDING VALVED CONDUITS FOR SELECTIVELY TRANSFERRING SAID RESIN MIXTURE AND A QUANTITY OF SAID SUCROSE SOLUTION FROM SAID SERVICE COLUMNS TO SAID REGENERATING COLUMN, MEANS FOR ADDING A LIQUID TO SAID REGENERATING COLUMN TO ADJUST THE SPECIFIC GRAVITY OF THE SUCROSE SOLUTION TO A VALUE INTERMEDIATE THE SPECIFIC GRAVITIES OF SAID ANION AND CATION RESINS WHEREBY ONE OF SAID RESINS FLOATS IN SAID SOLUTION WHILE THE OTHER SETTLES OUT, 